JPH1129851A - Production of accessories and accessories obtained with this method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain accessories having high class view, beautiful color tone and gloss in a low cost by melting titanium or titanium alloy with a crucible levitation method, producing precision casting product having complicate shape with a reduced pressure sucking-up casting and forming a film on this surface with ion plating. SOLUTION: A good permeable mold 7 forming a sucking-up hole 11 at the lower end is set to a chamber 12 and the sucking-up hole 11 is dipped into molten titanium or titanium alloy 6 melted with the crucible levitation melting method. Then, the molten metal 6 is sucked up into the mold 7 by reducing the pressure in the chamber 12 to produce the precision casting product. After removing the hardened layer on the surface of the casting product obtd. in such a way as barrel polishing, etc., in the case of necessity, the metallic film is formed by an ion plating method. As the ion plating method, the conventional method is used, and e.g. a hollow cathode discharging method (HCD method) is recommended.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing accessories such as rings, piercings, bracelets, and pendants having a metal coating, particularly a titanium coating, and to accessories manufactured by the method.

[0002]

2. Description of the Related Art Titanium and its alloys have excellent features such as light weight, high strength, heat resistance and corrosion resistance, and thus are widely used in the fields of aerospace, marine and chemical plants. In addition, with the advance of casting technology, titanium or titanium alloy has come to be frequently used for golf clubs, tennis racket frames, eyeglass frames, and the like. However, pure titanium is sticky, and the titanium alloy is hard, so that cutting is difficult. Further, since the melting point is as high as 1,700 ° C. or more, there is a problem that titanium is easily contaminated by reacting with air at the time of melting. In addition, in the conventional method, when melting in a vacuum to prevent oxidation of titanium or titanium alloy, a water-cooled copper crucible is used, and as a heat source, an arc, plasma or cold hearth melting using an electron beam is mainly used. In the melting method, heat is applied from the free surface of the molten metal, and the lower part is in large contact with the water-cooled copper crucible, so that the temperature of the molten metal is not uniform and the temperature of the molten metal is low overall. In addition, there is a time loss of several seconds from the stop of the heating to the start of the casting, during which the temperature of the molten metal may drop. Further, when the shape of the mold is complicated, the molten metal may not reach the end of the mold, so that centrifugal force casting must be used to turn the molten metal to the corner of the mold. Therefore, it has been extremely difficult to manufacture articles having a small size and a complicated shape, such as accessories, from titanium or a titanium alloy by a casting method.

[0003]

However, in recent years, a so-called levitation melting method in which a metal floats in a space and melts has come into practical use. The levitation melting method is a method of fusing and melting a metal in a magnetic field formed by a high-frequency induction coil. Levitation of metal is due to repulsion (Lorentz repulsion) acting between the coil current and the metal skin current having a different phase. The advantages of this dissolving method are that it is easy to dissolve non-contamination, raise the temperature of the molten metal and make the components uniform. Further, instead of the coil system, a so-called cold crucible system in which a plurality of insulating slits are provided vertically in a water-cooled copper crucible and a skin current flows through each segment to form a strong magnetic field inside the crucible has been put to practical use. According to this method, for example, 2
A large amount of metal, such as kg, can be dissolved by floating or point contact. When titanium or titanium alloy is melted by this cold crucible method, the molten metal does not come into contact with the crucible, so a high-temperature molten metal can be easily obtained, and contamination due to contact of the molten metal with the crucible is completely eliminated. can do. As described above, it has become possible to relatively easily dissolve titanium or a titanium alloy. However, as described above, another method is required to cast a complex-shaped casting using the molten metal. .

[0004]

Means for Solving the Problems As a casting method itself, a permeable mold having a molten metal suction port formed at a lower end is set in a chamber, and the suction port is immersed in the molten metal to reduce the pressure in the chamber. The so-called vacuum suction casting, in which the molten metal is sucked into a mold by a pressure difference between the inside and outside of the chamber, is known (Japanese Patent Publication No. 52-38924). The present inventors combined melting of titanium or a titanium alloy by the above-described crucible type levitation melting method and vacuum suction casting to cast accessories having a complicated shape, and ion-plating the surface of the obtained casting by ion plating. By forming a titanium film, we succeeded in manufacturing various accessories with beautiful colors and luster with high quality at low cost. That is, according to the present invention, (1) a breathable accessory mold having a suction port formed at a lower end is set in a chamber, and the suction port is placed in a molten titanium or titanium alloy melted by a crucible-levitation melting method. Manufacturing a precision casting by immersing the chamber into a mold by reducing the pressure of the chamber to produce a precision casting, and forming a coating on the surface of the casting by ion plating. And (2) an accessory manufactured by the manufacturing method of (1).

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The crucible used in the crucible levitating dissolution method of the present invention is a copper-made cylindrical or cylindrical water-cooled crucible with a bottom drawing. The inner wall surface of the crucible is provided with 6 to 36 insulating slits in the vertical direction. The inner diameter of the crucible is preferably about 20 to 100 mm. If the inner diameter is larger than 100 mm, it becomes difficult to float the metal, and the temperature of the molten metal becomes low. A graphite plug may be inserted into the bottom of the crucible. Titanium or a titanium alloy such as TiAl, TiNi, Ti6Al4V titanium is placed on the crucible. The crucible is desirably placed in an atmosphere of an inert gas such as argon to prevent oxidation of the molten metal. The output of the melting furnace power supply is usually 30 ~
The power is about 100 kW, preferably about 60 kW, and the frequency is about 20 to 50 kHz, preferably about 30 kHz.
The temperature in the crucible is 100 to several hundred degrees Celsius
It is desirable to raise the temperature to a temperature exceeding 1,800 ° C. in the case of titanium and generally slightly lower in the case of a titanium alloy. As a material of the mold, yttria-based, zirconia-based, calcia-based ceramics and the like are generally used, but yttria-based and zirconia-based ceramics are preferable. A mold having a complicated structure can be manufactured by using an air-permeable ceramic shell mold by a so-called lost wax method. The mold has a suction port provided at the lower end and is set in a confidential chamber provided with a gas suction outlet. When the suction port is immersed in the molten metal and the gas in the chamber is suctioned and discharged from the gas suction port, the pressure in the chamber is reduced, and the pressure in the air-permeable mold is also reduced. It is sucked into the mold. The wicking of the molten metal can be performed instantaneously, and since the temperature of the molten metal is high, the molten metal can reach the details of a complicated mold. When the pressure is released when the molten metal has reached the end of the mold, when the pressure is released, the molten metal remaining in the sprue portion above the suction port and not flowing into the mold is returned to the crucible again. The mold is allowed to cool, removed from the chamber, and sand cast to give a casting.

[0006] Since a hardened layer containing oxygen called α-case which is generated by the reaction with the mold exists on the surface of the fine titanium casting, it is removed by a mechanical barrel treatment or a chemical polishing treatment using hydrofluoric nitric acid. Is good. If necessary, the porosity existing inside the fine cast product is rendered harmless by HIP processing. If further welding is required, it is performed in an inert atmosphere such as argon. In the present invention, a metal film is formed on the cast product thus obtained by ion plating. Ion plating is a method known per se in which vaporized particles ionized in a vacuum reach a substrate to form a metal or ceramic film. The ion plating is performed by multi-cathode thermionic irradiation, high-frequency excitation (RF), hollow cathode discharge (HCD), cluster (ICB), activated reactive vapor deposition (ARE), and arc discharge. (AIP method) is known, but any of those methods may be used in the present invention. These ion platings have the following features in common. Immediately before the formation of the film, dirt and oxide film on the substrate surface are removed by bombardment using the discharge of an inert gas, and the film can be formed on the clean surface substrate without breaking the vacuum thereafter. The kinetic energy of the particles is increased by ionization of the evaporated particles, and the adhesion and characteristics of the film can be improved. Also in the process of forming the film, the substrate is sputtered by the ionized evaporated particles, and the mixing layer between the base material and the coating material is formed at the interface, so that the film is densified. By the ionization of the evaporated particles, the reactivity with the gas is increased, and a compound film such as a ceramic can be formed. For example by reactive ion plating, evaporation of Ti, N ₂ or by further introducing this and a small amount of C ₂ H ₂ gas, TiN or TixNyCz (x, y and z are x + y + z
(Positive number satisfying = 1), the color tone and gloss can be changed.

Therefore, this ion plating is most suitable for forming a beautiful and robust film on the surface of an accessory having a complicated shape as in the present invention. An electron gun is used as an evaporation source for ion plating. According to this electron gun, since a high temperature is obtained, almost all high-melting-point materials can be evaporated at a very high speed regardless of metals and ceramics. Generally, an evaporation material such as titanium is put in a water-cooled copper hearth, and the electron gun is turned at 180 ° or 270 °.
It can be bent, squeezed, repositioned, or shaken by the applied magnetic field by the deflection. Necklaces, piercings, rings,
Includes all kinds of metallic jewelry, including bracelets, chokers, pendants, brooches, and buckles.

[0008]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto. Example 1 As shown in FIG. 1, a water-cooled copper crucible 2 (outer diameter 82 mm, inner diameter 54 mm, height 80 mm, number of insulating slits 12) provided with a cooling water passage 1 was housed in a crucible housing chamber 3. . About 500 g of titanium powder was put in a crucible, argon gas 4 was sealed in the crucible accommodation chamber, and heated by a high frequency induction coil 5 (60 kW) to obtain a molten metal 6 at 1800 ° C. On the other hand, a mold 7 is a gas-permeable hollow mold produced by coating a surface of a ring prototype (not shown) made of wax with molding sand in multiple layers and heating it to melt the wax. It is. Each part of the mold is provided with a sprue 8, a gate 9, a cavity 10, and a suction port 11. When the suction port of the mold is immersed in the molten metal and forcedly sucked from the suction port 13 of the mold accommodating chamber 12 by a vacuum pump, the pressure in the mold chamber and the mold is reduced, and the molten metal quickly passes through the gate to fill each cavity. Fill to the tip. After the metal has solidified, the pressure in the cavity is released, and the mold is removed from the chamber and sand-sanded to obtain a precision titanium casting. This casting is
After cutting, mechanical barrel polishing, etc., if necessary, a film is formed on the surface by ion plating. The ion plating was performed by a so-called HCD method using pure titanium as an evaporation material and using a hollow cathode electron gun as an evaporation source. A ring having a golden-colored TiN film was manufactured by introducing N ₂ gas during ionization of the evaporated titanium particles.

[0009]

The effects of the present invention can be expressed by the following features of the product obtained by the present invention. 1. It has a high-quality beautiful finish and glossy finish. 2. No corrosion or deterioration due to sweat or normal environment. 3. Excellent abrasion resistance and maintains initial gloss for a long time. 4. The adhesion between the base and the film is high and the film does not peel off. 5. Despite being lightweight, the dimensional accuracy of the substrate can be maintained even if a film is formed. 6. There is no unevenness in the unevenness of the complicated shape part and the film on the front and back. 7. Due to low thermal conductivity, there is no cold feeling when worn. 8. Metal allergy to the skin is less likely to occur. 9. Manufacturing costs are low, including the steps before and after precision casting and skin formation.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an apparatus of a cold crucible type levitation melting method and a vacuum suction type precision casting method.

[Explanation of symbols]

 1. 1. Cooling water passage 2. Water-cooled copper crucible Crucible storage chamber 4. Argon gas 5. 5. High frequency induction coil Molten metal 7. 7. Mold Sprue 9. Gate 10. Cavity 11. Suction port 12. Mold containing chamber 13. Air intake

Claims (2)

[Claims] 1. A breathable accessory mold having a suction port formed at a lower end thereof is set in a chamber, and the suction port is immersed in a molten titanium or titanium alloy melted by a crucible levitation melting method. A method for manufacturing an accessory having a coating, characterized in that a molten metal is sucked into a mold by reducing the pressure in the chamber to produce a precision casting, and a coating is formed on the surface of the casting by ion plating. 2. An accessory manufactured by the method of claim 1.